Molecular differentiation between field lumpy skin disease isolate and Capripoxvirus vaccinal strains in Egypt 2018

Abstract

Lumpy skin disease virus is a member of the Capripoxvirus genus of the Poxviridae family, which affects cattle and causes a notifiable disease with significant economic losses. It is controlled by vaccination with capripox live attenuated vaccines. The aim of the study was the isolation and identification of the lumpy skin virus field virus strain during 2018. Nodular skin lesions were collected from clinically infected lumpy skin disease cattle that were used for the virus isolation on the chorioallantoic membrane of specific pathogen free embryonated chicken eggs and Madin Darby Bovine Kidney tissue culture. Polymerase chain reaction targeting the Capripoxvirus CaPV ORF103 gene was applied on the isolated virus and three Capripoxvirus vaccinal strains (Kenyan sheep pox virus, Held goat pox virus and Ismailia lumpy skin disease virus). The amplicons of the four strains of Capripoxvirus (one isolated and three vaccinal strains) were used for sequencing. Reference capripox viruses were obtained from GenBank to create the phylogenetic tree. The virus isolated from the collected nodular skin samples on chicken eggs showed clear typical pock lesions on the chorioallantoic membrane and on tissue cultures and showed a characteristic cytopathic effect. Positive samples of the isolated strain were identified by PCR for the CaPV ORF103 gene that yielded expected amplicon sizes of 570 bp. This was confirmed through gene sequence and analysed by BLAST, and submitted to GenBank under accession number MW 546997_LSD_Aziz_LSD. The phylogenetic tree revealed that the field isolate strain of LSDV had different identity percentages ranging from 98.2–99.8% with the tested vaccinal Capripoxvirus strains in Egypt. The amino acid sequence showed only different amino acid found in the field isolate strain and not in other tested vaccinal strains, and a maximum homology (100%) of the isolated strain nucleotide sequence was with two GenBank recorded strains. We recommend maintaining the routine lumpy skin disease vaccination programme in Egypt, frequent eradication of the insect population, and further genetic studies on the genomes of this virus strain and the Capripoxvirus vaccinal strains to reach the most related and homologous vaccinal strain given the massive genome of this disease.